It looks like the Europa League or bust now for Manchester United 's Champions League qualification hopes.

And the Red Devils’ European ­challenge was made all the harder during Sunday's home draw with relegation candidates Swansea by injuries to Eric Bailly and Luke Shaw — the former ­leaving Mourinho without any recognised central defenders for the semi-final first leg against Celta Vigo.

Bailly joins fellow centre-halves Phil Jones, Chris Smalling and Marcos Rojo on the sidelines, leaving Mourinho to once again bemoan the fixture pile-up he believes is the cause of so many injuries.

“At the moment we can’t walk from the bed to the toilet without breaking a leg,” said the manager.

Bailly is now set to miss the first leg against Celta Vigo on Thursday... (Image: PA Wire)

...just like the rest of Mourinho's central defenders (Image: PA)

Every time they have had the top-four in sight this season, United have slipped up, as if an attack of vertigo leaves them unable to climb into the Champions League places.

It was a familiar story again against the Swans at Old Trafford, as they registered a 10th home draw in the Premier League this season — a total of 23 points dropped, including the defeat to direct top-four race Manchester City.

They may have stretched their ­unbeaten run in a single season to a club-record 25 games, but it was no cause for celebration.

After this latest missed opportunity, Thursday’s tie in northern Spain has assumed even greater significance.

Mourinho was also without Zlatan Ibrahimovic, Tim Fosu-Mensah, Paul Pogba and the suspended ­Marouane Fellaini, although the latter two will be back to face Celta.

The Portuguese even threatened to play a weakened team at home to Crystal Palace on the final day of the top-flight season if United are in the ­Europa League final three days later.

“It’s a consequence of our ­success, but also of the ­calendar,” he said. “You are ­punished for doing well.

United's injury woes deepened even further when Shaw was hurt against Swansea... (Image: Reuters)

...forcing a substitution after just nine minutes of the match (Image: Action Images via Reuters)

"At the moment this is hypothetical, but if we beat Celta, we have the final. But the Europa League final is on the Wednesday (May 24) and we play ­Palace on the Sunday, and ­Southampton a few days before that (on the 17th).

“We could be playing the final with disastrous consequences.

"Maybe I will bring Nicky Butt and his team (United's Under-23s) to play against Crystal Palace.And hopefully Palace (six points above the relegation places with three games to go) doesn’t need to stay in the ­division, ­because it would be very bad if they needed the points and we played our Under-23s.”

For Swansea, this was a vital point in their ongoing battle for survival, even if they had to ­suffer the injustice of conceding from a first-half penalty that should never have been given.

Marcus Rashford did not need an invitation to tumble to the turf when Lukasz Fabianski came charging off his line towards him, although the keeper tried to pull out of the challenge.

Swansea were outraged when this was ruled to be a penalty (Image: Action Images via Reuters)

Rashford hooked his right leg over Fabianski’s outstretched arms, looking for the spot-kick, which referee Neil Swarbrick duly gave, after pausing to ­consider his decision.

Replays of the incident ­vindicated the ­indignity of Swansea’s players, with Rashford clearly drawing the foul.

United skipper Wayne Rooney, who did little else on an afternoon which showed just why his 13-year Old Trafford ­career will come to an end this summer, stepped up to convert from the spot.

It was Rooney’s 252nd goal for the club, but it was not enough to secure the win they needed to ensure they kept pace with their rivals in the race for a ­top-four spot.

Skipper Rooney cashed in on the officials' error to put United in front... (Image: REUTERS)

...but his 252nd Reds goal was not enough for a win as they dropped more home points (Image: Rex Features)

In fact, it was Rooney who ­fulfilled the role of United ­fall-guy, conceding the free-kick from which the Swans scored with a needless foul on Jordan Ayew 20 yards out.

With a dead-ball specialist of Gylfi Sigurdsson’s expertise, it was arguably the worst possible place to concede a set-piece.

The Icelandic star left keeper David De Gea rooted to his line, as he curled the ball around the wall and into the net, at the exact spot Ander Herrera had briefly been standing after dropping back to the post, before returning to the wall.

It was a majestic strike that yielded a deserved point for Paul ­Clement’s side.